A few build Q's

[JTDay]

8-23-10 Two questions listed in new post..


As far as machining goes I plan on having the head cleaned, resurfaced, and checked for deformities. Then I will replace valve stem oil seals and cam seal then reassemble. That's where my first question is:

1. Once I reassemble the head, how do I know the proper position to put the cam pulley back on. I know there are line-up marks on the pulley and the head but wont the position of the camshaft affect this? Or is there a special position the cam is supposed to be rotated at before I put pulley on and line up marks? ANSWERED

2. What is the safe/proper way to clean the internal head parts like rockers, rocker shafts, cam, etc. ?ANSWERED

3. What lubes n' shit do I have to use and on what surfaces do I put them on when I reasseble the head? . ANSWERED



Thanks to all who take the time to read this (my apologies for typos).
-Josh D.

[hotballs]

seriously?

[Sagaris]

I recently saw a 90k mile M20b25 on my local craigslist for sale for $700, looks like its gone now but If I were in your position, I would be afraid about getting everything done and installed , thinking im done, then something expensive goes wrong and being out of time and money to fix it. I would rather buy a known good engine for ~$500, pop it in, and take your time refreshing the other engine correctly.

[jlevie]

The cam sprocket indexes to the cam via a pin, so there can't be any timing errors there. When it is time to put the head back on, position the engine at TDC and align the cam sprocket with the mark.

Dip type parts cleaner does a great job on cleaning parts. But simply washing the parts down with mineral spirits is sufficient.

There are assembly lubes available, but engine oil also works. Lube should be applied to every bearing surface during assembly.

Ideal clearance on the bottom end bearings is one ten thousandth per inch of journal diameter. Plasti-gage sort of works, but checking clearances is best done with a micrometer and a bore gage. It is also best to check the journals at several points to make sure they aren't worn. If acceptable, have the journals polished.

[JTDay]

I recently saw a 90k mile M20b25 on my local craigslist for sale for $700, looks like its gone now but If I were in your position, I would be afraid about getting everything done and installed , thinking im done, then something expensive goes wrong and being out of time and money to fix it. I would rather buy a known good engine for ~$500, pop it in, and take your time refreshing the other engine correctly.

This option never even crossed my mind. I'm 19 and a little impulsive. Appreciate the input.

The cam sprocket indexes to the cam via a pin(I can't believe I didn't realize this during disassembly), so there can't be any timing errors there. When it is time to put the head back on, position the engine at TDC and align the cam sprocket with the mark.

Dip type parts cleaner does a great job on cleaning parts. But simply washing the parts down with mineral spirits is sufficient.

There are assembly lubes available, but engine oil also works. Lube should be applied to every bearing surface during assembly.

Ideal clearance on the bottom end bearings is one ten thousandth per inch of journal diameter. Plasti-gage sort of works, but checking clearances is best done with a micrometer and a bore gage. It is also best to check the journals at several points to make sure they aren't worn. If acceptable, have the journals polished.

Thanks buddy.

[JTDay]

A few questions.

Regarding rear main seal install, I'm having a bit of trouble finding detailed instructions. Do I really need one of those seal installers? It seems superfluous for just putting a piece of rubber in a recessed opening. Also, once seal is pushed in, is it neccessary to apply RTV? I'm finding mixed reviews about rtv use and seals. ANSWERED

For head assembly I assume the only place assembly lube is needed are on the cam journal bearing surfaces. Is this correct?ANSWERED

[nando]

no, you can tap it in gently with a rubber hammer and a block of wood. don't put RTV on the seals, put some motor oil on the inside lip, and if you must, hylomar on the outside.

I'd put assembly lube wherever there is metal on metal contact. also prime the oil pump before you start it.

the M20 is about as simple of an engine to build as it gets. I wouldn't worry too much as long as you've done your homework.

[JTDay]

no, you can tap it in gently with a rubber hammer and a block of wood. don't put RTV on the seals, put some motor oil on the inside lip, and if you must, hylomar on the outside.

I'd put assembly lube wherever there is metal on metal contact. also prime the oil pump before you start it.

the M20 is about as simple of an engine to build as it gets. I wouldn't worry too much as long as you've done your homework.

Thanks, is there a good online reference for priming the oil pump?

Also is it ok to use roller and paint brush cleaner/stripper on the head parts? It seems to be pretty heavy duty with cautions and warnings about carcinogens and birth defects from fumes and whatnot.

[jlevie]

To prim the oil system, remove the cap on the left side of the engine where a mechanical distributor would mount. Fish out the oil pump gear and use a 6mm (I think) socket on long extensions on the oil pump drive shaft spun with an electric drill.

[JTDay]

Got a bare head, all parts cleaned. I ended up using paint brush cleaner which appears to be nearly straight turpentine. I am now in the process of removing everything from the short block, which leads to my next question:

Is there a general rule of thumb as to which bolts receive anti-seize/loctite and which go in bare?

And as for the rear seal carrier, can I just pull/pry/pound it out with a flathead screwdriver or will that cause dammage to anything? ANSWERED

[JTDay]

bump

[JTDay]

I noticed that there are these metal jacket things in between the head and block where the head bolts slide through. There are only two of them, one on exhaust side and one on intake side. Could someone verify that I dont need any more of these things?

Thanks

EDIT: knew id forget something. The bentley manual says to tighten eccentric bolts to 89 in lbs. which converts to about 7.4 ft lbs. This seems to little for something under so much pressure. Could someone pleaes verify this as well?

[nando]

it doesn't take much. Basically, hand tight. If you tighten too hard, they strip pretty easy. I'd actually reccomend all new nuts/bolts for the eccentrics. Also check the clips that hold the rockers for wear and springyness. I had some worn ones and some that had no "spring" left in them, so the rockers moved around a lot.. noisy!

as far as the "jackets", they're locating dowels for the head. you only need 2. but make sure they are there so the head goes on straight!

[JTDay]

Thanks to all for the help. I'm about ready to start putting things back together, but I'm missing a few of those dowels and cant find what size they are ANYWHERE.

One is the head centering dowel that goes in between the block and head and the other is the one on the front of the head, intake side. Pelican lists sizes as 8.5mm, 10.5mm, 12.5mm, and 14.5mm (split and solid-ring) and all are for "various applications". Which ones do I need for the head?

[nando]

https://www.realoem.com/bmw/

try that, if it doesn't say the size you can cross reference the part # on pelican. remember that E30s are in the "archive" section.